It is often desirable to remove a layer from a solid substrate, such as concrete pavement, metal decks, fiberglass decks and the like, to prepare the surface for a subsequent finish coating such as painting, sealing or retopping. A hand operated concrete surface treatment apparatus is disclosed in U.S. Pat. No. 3,156,231. A rotary cutter cage for the apparatus carries a plurality of star-shaped cutter elements. During rotation of the cutter cage, the cutter elements impact the concrete surface to chip away a layer from the surface. A larger self-propelled surface conditioning machine is disclosed in U.S. Pat. No. 3,266,846. The apparatus includes a rotary cutter cage having several cutter elements. The cutter cage is rotated and transported across the surface to be treated to remove a layer of material from the surface. Other examples of concrete milling machines or planars using star-shaped cutter elements are disclosed in U.S. Pat. Nos. 3,063,690 and 3,156,231. In U.S. Pat. No. 3,156,231, the series of circular star cutter wheels, as mounted on a bar of the cutter cage, are held in place by the use of crimped washers or the like beyond the extreme ends of the pack. Such crimped washers serve to center and locate the series of cutter elements on each bar of the cutter cage.
U.S. Pat. No. 2,795,176 discloses a pulverizing machine for use in treating hard substrates, such as concrete. The system pulverizes the surface by rapidly rotating tools or hammers which impact the surface over which they travel. Springs are used at the base of each hammer, as pivotally connected to a drive shaft, to yieldably position the hammer in a radially outwardly extending position. This enables each arm to yield in case of impact against an underlying hard object, as well as to yield in response to inertia during the starting and stopping of the shaft, thus permitting smoother operation of the machine.
In the operation of surface treatment systems, such as disclosed in U.S. Pat. No. 3,063,690, the star-shaped cutters rotate at high speeds relative to the bars on which they are mounted. This is due to the contacting of the star-shaped cutters with the solid substrate causing the cutters to rotate at high speeds relative to the bars in a direction opposite to the direction of rotation of the cutter cage. The apparatus, according to this invention, prevents continued rotation of the cutters on the cutter cage to significantly improve the efficiency and effectiveness of the cutter elements in removing material from the solid substrate being treated.